Re: [Intel-gfx] [PATCH] drm/i915/tgl+: Fix Combo PHY DPLL fractional divider for 38.4MHz ref clock

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jul 14, 2020 at 07:32:36PM +0300, Imre Deak wrote:
> Apply Display WA #22010492432 for combo PHY PLLs too. This should fix a
> problem where the PLL output frequency is slightly off with the current
> PLL fractional divider value.
> 
> I haven't seen an actual case where this causes a problem, but let's
> follow the spec. It's also needed on some EHL platforms, but for that we
> also need a way to distinguish the affected EHL SKUs, so I leave that
> for a follow-up.
> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 54 +++++++++++++++++--
>  1 file changed, 49 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> index aeb6ee395cce..aee9101f5e7c 100644
> --- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> +++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> @@ -2887,7 +2887,7 @@ static const struct icl_combo_pll_params icl_dp_combo_pll_24MHz_values[] = {
>  };
>  
>  
> -/* Also used for 38.4 MHz values. */
> +/* On ICL also used for 38.4 MHz values. */
>  static const struct icl_combo_pll_params icl_dp_combo_pll_19_2MHz_values[] = {
>  	{ 540000,
>  	  { .dco_integer = 0x1A5, .dco_fraction = 0x7000,		/* [0]: 5.4 */
> @@ -2915,6 +2915,37 @@ static const struct icl_combo_pll_params icl_dp_combo_pll_19_2MHz_values[] = {
>  	    .pdiv = 0x1 /* 2 */, .kdiv = 1, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
>  };
>  
> +/*
> + * Display WA #22010492432: tgl
> + * Divide the nominal .dco_fraction value by 2.
> + */
> +static const struct icl_combo_pll_params tgl_dp_combo_pll_38_4MHz_values[] = {
> +	{ 540000,
> +	  { .dco_integer = 0x1A5, .dco_fraction = 0x3800,		/* [0]: 5.4 */
> +	    .pdiv = 0x2 /* 3 */, .kdiv = 1, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
> +	{ 270000,
> +	  { .dco_integer = 0x1A5, .dco_fraction = 0x3800,		/* [1]: 2.7 */
> +	    .pdiv = 0x2 /* 3 */, .kdiv = 2, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
> +	{ 162000,
> +	  { .dco_integer = 0x1A5, .dco_fraction = 0x3800,		/* [2]: 1.62 */
> +	    .pdiv = 0x4 /* 5 */, .kdiv = 2, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
> +	{ 324000,
> +	  { .dco_integer = 0x1A5, .dco_fraction = 0x3800,		/* [3]: 3.24 */
> +	    .pdiv = 0x4 /* 5 */, .kdiv = 1, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
> +	{ 216000,
> +	  { .dco_integer = 0x1C2, .dco_fraction = 0x0000,		/* [4]: 2.16 */
> +	    .pdiv = 0x1 /* 2 */, .kdiv = 2, .qdiv_mode = 1, .qdiv_ratio = 2, }, },
> +	{ 432000,
> +	  { .dco_integer = 0x1C2, .dco_fraction = 0x0000,		/* [5]: 4.32 */
> +	    .pdiv = 0x1 /* 2 */, .kdiv = 2, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
> +	{ 648000,
> +	  { .dco_integer = 0x1FA, .dco_fraction = 0x1000,		/* [6]: 6.48 */
> +	    .pdiv = 0x2 /* 3 */, .kdiv = 1, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
> +	{ 810000,
> +	  { .dco_integer = 0x1A5, .dco_fraction = 0x3800,		/* [7]: 8.1 */
> +	    .pdiv = 0x1 /* 2 */, .kdiv = 1, .qdiv_mode = 0, .qdiv_ratio = 0, }, },
> +};
> +
>  static const struct skl_wrpll_params icl_tbt_pll_24MHz_values = {
>  	.dco_integer = 0x151, .dco_fraction = 0x4000,
>  	.pdiv = 0x4 /* 5 */, .kdiv = 1, .qdiv_mode = 0, .qdiv_ratio = 0,
> @@ -2950,13 +2981,26 @@ static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
>  				  struct skl_wrpll_params *pll_params)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(crtc_state->uapi.crtc->dev);
> -	const struct icl_combo_pll_params *params =
> -		dev_priv->dpll.ref_clks.nssc == 24000 ?
> -		icl_dp_combo_pll_24MHz_values :
> -		icl_dp_combo_pll_19_2MHz_values;
> +	const struct icl_combo_pll_params *params;
>  	int clock = crtc_state->port_clock;
>  	int i;
>  
> +	switch (dev_priv->dpll.ref_clks.nssc) {
> +	case 19200:
> +		params = icl_dp_combo_pll_19_2MHz_values;
> +		break;
> +	case 24000:
> +		params = icl_dp_combo_pll_24MHz_values;
> +		break;
> +	case 38400:
> +		/* TODO: Apply WA #22010492432 on EHL too. */
> +		if (IS_TIGERLAKE(dev_priv))
> +			params = tgl_dp_combo_pll_38_4MHz_values;
> +		else
> +			params = icl_dp_combo_pll_19_2MHz_values;
> +		break;
> +	}

Hmm. This only takes care of DP AFAICS. What about HDMI?
Also doesn't readout need some tweaking too?

Should we rather consider pushing this w/a deeper into
the register progamming/readout code?

> +
>  	for (i = 0; i < ARRAY_SIZE(icl_dp_combo_pll_24MHz_values); i++) {
>  		if (clock == params[i].clock) {
>  			*pll_params = params[i].wrpll;
> -- 
> 2.23.1
> 
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-- 
Ville Syrjälä
Intel
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